Field of the Invention
This invention relates to a tack roll tool for expanding the ends of heat exchanger tubes into intimate contact with openings through a tube sheet of a steam generator and more particularly to such a tool and tool support therefor for remote automatic operation within a nuclear steam generator.
2. Description of the Prior Art
Retubing of a steam generator generally includes a procedure for initially placing the heat exchanger tube ends flush with the lower face of a tube sheet and manually tack rolling the tube end (e.g. expanding the diameter of the tube wall by an internal tube expansion tool) so as to provide intimate contact to retain the tube in proper position in the tube sheet for subsequent welding therebetween.
In a normal steam generator such operation can be done manually and the tack roll tool generally comprises a pistol-like hand-held reversible air motor having a tool chuck for receiving the expanding-roller tool head which in turn comprises an axially extending, rotatable, conically tapered mandrel and a plurality of generally cylindrical roller members mounted in slantwise relationship thereon by a mandrel cage so that rotation of the mandrel causes the rollers to roll against the tube wall and, as the wall diameter expands, the increasing diameter of the tapered mandrel causes the rollers to move further radially outwardly to continue the expansion procedure. In such manual tool, the collar of the tool chuck has a flat face for engaging the tube end extending below the lower face of the tube sheet, and the tool is disposed within the tube. The tube and tool are thus manually lifted until the chuck face contacts the bottom face of the tube sheet. Further upward movement of the air motor pistol grip (while the chuck and tool remain stationary) permits air valving internal to the air motor to initiate forward rotation of the tool head to accomplish the tack rolling. As the tube is expanded into engagement with the tube sheet the torque required by motor is increased. Upon a preset torque being attained, the tool head stops automatically and a manually operated reversing trigger is depressed to reverse the air motor to free the tool from the expanded tube and ready for the next expansion process. Such an air driven tube expansion torque control tool is commercially available from the Tool Group Marketing Division of Dresser Industries Inc. and identified as Airetool Model 810, in Airetool Tube Expander Catalog #E-3-10.
However, in the environment of an irradiated nuclear steam generator the manual procedure described above must be accomplished by a remotely operated tool in order that presence of repair personnel within the generator is minimized. Further, because of certain internal structure of the nuclear steam generator and because of the desirability for unimpeded maneuverability of the tool, the pistol-like air motor and tool chuck cannot be maintained together in axial vertical alignment without causing interference with certain other structure of either the generator or the tool support.